1. Field of the Invention
The present invention relates to a braking system for a motor vehicle, which includes both of a frictional braking device and a regenerative braking device.
2. Discussion of the Related Art
An example of a vehicle braking system of the type indicated above is disclosed in JP-A-6-171489. The frictional braking device is arranged to apply a frictional braking torque to each of a plurality of wheels of the vehicle, by frictional engagement of a friction member with a rotor which rotates with the wheel. On the other hand, the regenerative braking device is arranged to apply a regenerative braking torque to at least one drive wheel of the vehicle, by regenerative braking by at least one electric motor connected to the above-indicated at least one drive wheel. In the vehicle braking system including both of these frictional and regenerative braking devices, each of the wheels is braked with a total braking torque which includes at least one of the frictional braking torque and the regenerative braking torque. When the total braking torque of a given wheel has exceeded an upper limit corresponding to a friction coefficient of a road surface, the frictional braking device for that wheel is controlled in an anti-lock fashion, so that the frictional braking torque is controlled so as to hold the wheel in a substantially optimum slipping state, while the regenerative braking torque is held zero.
In the vehicle braking system disclosed in the above-identified publication, the anti-lock control of the frictional braking device for the drive wheel has a problem such as insufficiency of the total braking torque due to zeroing of the regenerative braking torque.